The present invention relates generally to optically-read digital recording discs. More specifically, the present invention relates to reconditioning the protective surface of digital recording discs.
Optically-read digital recording discs, including compact discs (CDs), digital versatile discs (DVDs), CD-ROMs, recordable CDs (CD-Rs), re-writable CDs (CD-RWs), and the like, are widely used to store different types of information. Digital recording discs may be formatted for use with audio, video, or computer equipment that reads the data recorded on the discs. The technology associated with digital discs and digital playback equipment is well known to those skilled in the art. Basically, digital information is encoded and arranged in spiral data tracks within the disc beneath an optically transparent protective layer, or surface, of plastic. A laser beam reads the digital information during playback, and the information is then processed and presented to the user in the form of sound, visual images, or computer data.
The optically transparent protective surface forms the bulk of the thickness and weight of the disc. Generally, the protective surface protects the data layer from damage on the play side. In addition, the protective surface acts as a transparent substrate to support the data layer of the disc. Damage or surface imperfections located on the transparent protective surface can interfere with the laser beam before it reaches the data layer. Although modern playback devices include error correction techniques, this interference can prevent the player from reading the data correctly, or at all, resulting in audible problems, even though the data layer itself is undamaged. Due to the high cost of digital discs, it is desirable to repair such damaged discs rather than replace them.
In recent years, the disc reclamation industry has prospered due to the widespread use and longevity of digital recording discs. However, many used discs cannot be resold because scratches on the protective surface render them unplayable or visually unappealing. Consequently, to improve disc playability and visual appeal, various methods for treating the surface of a CD have been developed. However, these prior art methods suffer from several disadvantages.
One known process for reconditioning digital recording discs involves a motorized apparatus having a buffing surface that abrades the protective surface in a generally uniform manner across the surface area of the disc. While this method may effectively repair the protective surface of some discs, it can leave fine abrasions on other discs so that visual appeal is not restored. Moreover, the fine abrasions can fall into alignment with the spiral data track or otherwise affect the optical tracking quality of the treated disc so that playability is not restored.
Another problem with prior art disc reconditioning devices is that they can leave a ridge-like abrasion pattern. That is, following reconditioning there is a sudden, or stepwise, change between the thickness of an unconditioned portion of the protective surface and a reconditioned portion of the protective surface. A laser beam passing through this sharp demarcation may be undesirably bent or scattered so that the underlying data track or tracks cannot be detected by the playback equipment.
The inability to restore playability may be exacerbated when reconditioning DVDs. DVD playback equipment employs a shorter wavelength laser than the other digital playback equipment. This DVD laser is capable of reading data tracks that are smaller and closer together than the data tracks that can be read by the conventional laser in CD players or CD-ROM drives. Because DVD data tracks are closer together, more of them can fit on a disc of the same size. Consequently, DVDs can hold about seven times as much data as an audio CD or a CD-ROM. Unfortunately, fine abrasions remaining on the DVD following reconditioning can adversely affect the playability of the more closely spaced DVD data tracks.
In addition, a non-uniform abrasion of the protective surface of the DVD can adversely affect the playability of the DVD data tracks following reconditioning. Non-uniform abrasion of the protective surface can occur when polishing DVDs using a motorized apparatus that rotates a foam-backed buffing pad. In particular, as the foam-backed buffing pad presses against the protective surface of the DVD, the periphery of the buffing pad compresses more than the central portion of the buffing pad. Such a situation happens because the foam surrounding the central portion of the foam-backed buffing pad supports the central portion so that it is more resistant to compression than the peripheral portion of the foam-backed buffing pad. The resistance to compression produces a greater buffing force against the central portion of the DVD than the buffing force against the peripheral portion of the DVD. Accordingly, this non-uniform buffing force can result in more abrasion at the central portion of the protective surface than at the peripheral portion of the protective surface to adversely affect the playability of the closely-spaced DVD data tracks.
Another result of the different laser in the DVD playback equipment is that the clear protective surface only needs to be about half as thick for a DVD as it does for an audio CD or CDROM. Hence, two DVDs can be placed back to back, resulting in two play sides and no label side, thereby further doubling the data capacity of a DVD. Since there is no label side, all manufacturer""s identification for the DVD is screen printed onto the narrow text band just outside of the clamping area, or stacking ring, of the DVD.
If a motorized reconditioning apparatus buffs the text band, the manufacturer""s identification will be undesirably abraded off leaving the DVD indistinguishable from other unmarked DVDs. This is highly undesirable when the DVDs are to be resold. Such a situation is also undesirable when the DVDs are used in a rental establishment because without the manufacturer""s identification on the text band, the DVDs can be easily confused with one another. Thus, there is a need for a disc reconditioning apparatus that abrades the protective surface in uniform manner across the surface area of the disc without damaging the text band on the digital recording disc.
Accordingly, it is an advantage of the present invention that an apparatus and buffing element are provided that restore both the playback quality and the visual appearance of an optically-read digital recording disc.
It is another advantage of the present invention that the apparatus and buffing element effectively recondition the protective surface of the disc without causing damage to the text band.
It is another advantage of the present invention that the buffing element imparts a substantially uniform buffing force against the protective surface of the disc.
It is yet another advantage of the present invention that the buffing element of the present invention produces an abrasion pattern with a gradual transition between unconditioned and reconditioned portions of the disc.
The above and other advantages of the present invention are carried out in one form by a buffing element in an apparatus for reconditioning a protective surface of an optically-read digital recording disc. The buffing element includes a foam pad having a discoid portion and an annular portion encircling a perimeter of the discoid portion, the annular portion being more resistant to compression than the discoid portion. A buffing pad is in fixed relation with the foam pad. The buffing pad has first and second surfaces on opposing sides of the buffing pad. The first surface is configured to face the foam pad, and the second surface is configured to contact and recondition the protective surface of the digital recording disc.
The above and other advantages of the present invention are carried out in another form by an apparatus for reconditioning a protective surface of an optically-read digital recording disc. The apparatus includes a turntable configured to receive a center section of the optically-read disc, the center section being located about a center hole of the optically-read disc. A first motor is coupled to the turntable and rotates the turntable and the optically-read disc at a first rotational speed. The apparatus further includes a buffing element for removing an amount of material from the protective surface as the turntable rotates the optically-read disc through at least one revolution. The buffing element includes a substantially rigid stabilizer plate having a plate surface. A first foam pad is fixedly engaged with the plate surface. The first foam pad has a discoid portion and an annular portion encircling a perimeter of the discoid portion, and the annular portion is more resistant to compression than the discoid portion. The buffing element further includes a second foam pad formed from closed cell foam and coupled to the first foam pad, and a buffing pad having first and second surfaces on opposing sides of the buffing pad. The first surface is configured to removably adhere to the second foam pad, and the second surface is configured to recondition the protective surface of the digital recording disc. A second motor is coupled to the buffing element and rotates the buffing element at a second rotational speed. A timing element, in communication with each of the first and second motors, synchronizes the first and second motors to substantially simultaneously cease rotation of the turntable and the buffing element following removal of the amount of material.